Move task_queue.* to base because it makes more sense there.

TEST=base_test --gtest_filter=TaskQueue*.* (added in this patch).
BUG=38475

Review URL: http://codereview.chromium.org/3205004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@57479 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 242 insertions, 0 deletions

diff --git a/base/base.gyp b/base/base.gyp
index 23e8c6b..d3ac910 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -144,6 +144,7 @@
         'sys_info_unittest.cc',
         'sys_string_conversions_mac_unittest.mm',
         'sys_string_conversions_unittest.cc',
+        'task_queue_unittest.cc',
         'thread_checker_unittest.cc',
         'thread_collision_warner_unittest.cc',
         'thread_local_storage_unittest.cc',
diff --git a/base/base.gypi b/base/base.gypi
index 2a6e64a..383e45d 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -253,6 +253,8 @@
           'sys_string_conversions_win.cc',
           'task.cc',
           'task.h',
+          'task_queue.cc',
+          'task_queue.h',
           'template_util.h',
           'thread.cc',
           'thread.h',
diff --git a/base/task_queue.cc b/base/task_queue.cc
new file mode 100644
index 0000000..e3c196b
--- /dev/null
+++ b/base/task_queue.cc
@@ -0,0 +1,49 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/task_queue.h"
+
+#include "base/logging.h"
+#include "base/stl_util-inl.h"
+
+TaskQueue::TaskQueue() {
+}
+
+TaskQueue::~TaskQueue() {
+  // We own all the pointes in |queue_|.  It is our job to delete them.
+  STLDeleteElements(&queue_);
+}
+
+void TaskQueue::Run() {
+  // Nothing to run if our queue is empty.
+  if (queue_.empty())
+    return;
+
+  std::deque<Task*> ready;
+  queue_.swap(ready);
+
+  // Run the tasks that are ready.
+  std::deque<Task*>::const_iterator task;
+  for (task = ready.begin(); task != ready.end(); ++task) {
+    // Run the task and then delete it.
+    (*task)->Run();
+    delete (*task);
+  }
+}
+
+void TaskQueue::Push(Task* task) {
+  DCHECK(task);
+
+  // Add the task to the back of the queue.
+  queue_.push_back(task);
+}
+
+void TaskQueue::Clear() {
+  // Delete all the elements in the queue and clear the dead pointers.
+  STLDeleteElements(&queue_);
+}
+
+bool TaskQueue::IsEmpty() const {
+  return queue_.empty();
+}
diff --git a/base/task_queue.h b/base/task_queue.h
new file mode 100644
index 0000000..5bfc777
--- /dev/null
+++ b/base/task_queue.h
@@ -0,0 +1,43 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_TASK_QUEUE_H_
+#define BASE_TASK_QUEUE_H_
+#pragma once
+
+#include <deque>
+
+#include "base/task.h"
+
+// A TaskQueue is a queue of tasks waiting to be run.  To run the tasks, call
+// the Run method.  A task queue is itself a Task so that it can be placed in a
+// message loop or another task queue.
+class TaskQueue : public Task {
+ public:
+  TaskQueue();
+  ~TaskQueue();
+
+  // Run all the tasks in the queue.  New tasks pushed onto the queue during
+  // a run will be run next time |Run| is called.
+  virtual void Run();
+
+  // Push the specified task onto the queue.  When the queue is run, the tasks
+  // will be run in the order they are pushed.
+  //
+  // This method takes ownership of |task| and will delete task after it is run
+  // (or when the TaskQueue is destroyed, if we never got a chance to run it).
+  void Push(Task* task);
+
+  // Remove all tasks from the queue.  The tasks are deleted.
+  void Clear();
+
+  // Returns true if this queue contains no tasks.
+  bool IsEmpty() const;
+
+ private:
+   // The list of tasks we are waiting to run.
+   std::deque<Task*> queue_;
+};
+
+#endif  // BASE_TASK_QUEUE_H_
diff --git a/base/task_queue_unittest.cc b/base/task_queue_unittest.cc
new file mode 100644
index 0000000..90fc4cd
--- /dev/null
+++ b/base/task_queue_unittest.cc
@@ -0,0 +1,147 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "base/task.h"
+#include "base/task_queue.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+// Sets bools according to whether Run or the destructor were called.
+class TrackCallsTask : public Task {
+ public:
+  TrackCallsTask(bool* ran, bool* deleted)
+      : ran_(ran),
+        deleted_(deleted) {
+    *ran_ = false;
+    *deleted_ = false;
+  }
+
+  virtual ~TrackCallsTask() {
+    *deleted_ = true;
+  }
+
+  virtual void Run() {
+    *ran_ = true;
+  }
+
+ private:
+  bool* ran_;
+  bool* deleted_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrackCallsTask);
+};
+
+// Adds a given task to the queue when run.
+class TaskQueuerTask : public Task {
+ public:
+  TaskQueuerTask(TaskQueue* queue, Task* task_to_queue)
+      : queue_(queue),
+        task_to_queue_(task_to_queue) {
+  }
+
+  virtual void Run() {
+    queue_->Push(task_to_queue_);
+  }
+
+ private:
+  TaskQueue* queue_;
+  Task* task_to_queue_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskQueuerTask);
+};
+
+}  // namespace
+
+TEST(TaskQueueTest, RunNoTasks) {
+  TaskQueue queue;
+  EXPECT_TRUE(queue.IsEmpty());
+
+  queue.Run();
+  EXPECT_TRUE(queue.IsEmpty());
+}
+
+TEST(TaskQueueTest, RunTasks) {
+  TaskQueue queue;
+
+  bool ran_task1 = false;
+  bool deleted_task1 = false;
+  queue.Push(new TrackCallsTask(&ran_task1, &deleted_task1));
+
+  bool ran_task2 = false;
+  bool deleted_task2 = false;
+  queue.Push(new TrackCallsTask(&ran_task2, &deleted_task2));
+
+  queue.Run();
+
+  EXPECT_TRUE(ran_task1);
+  EXPECT_TRUE(deleted_task1);
+  EXPECT_TRUE(ran_task2);
+  EXPECT_TRUE(deleted_task2);
+  EXPECT_TRUE(queue.IsEmpty());
+}
+
+TEST(TaskQueueTest, ClearTasks) {
+  TaskQueue queue;
+
+  bool ran_task1 = false;
+  bool deleted_task1 = false;
+  queue.Push(new TrackCallsTask(&ran_task1, &deleted_task1));
+
+  bool ran_task2 = false;
+  bool deleted_task2 = false;
+  queue.Push(new TrackCallsTask(&ran_task2, &deleted_task2));
+
+  queue.Clear();
+
+  EXPECT_TRUE(queue.IsEmpty());
+
+  queue.Run();
+
+  EXPECT_FALSE(ran_task1);
+  EXPECT_TRUE(deleted_task1);
+  EXPECT_FALSE(ran_task2);
+  EXPECT_TRUE(deleted_task2);
+  EXPECT_TRUE(queue.IsEmpty());
+}
+
+TEST(TaskQueueTest, OneTaskQueuesMore) {
+  TaskQueue main_queue;
+
+  // Build a task which will queue two more when run.
+  scoped_ptr<TaskQueue> nested_queue(new TaskQueue());
+  bool ran_task1 = false;
+  bool deleted_task1 = false;
+  nested_queue->Push(
+      new TaskQueuerTask(&main_queue,
+                         new TrackCallsTask(&ran_task1, &deleted_task1)));
+  bool ran_task2 = false;
+  bool deleted_task2 = false;
+  nested_queue->Push(
+      new TaskQueuerTask(&main_queue,
+                         new TrackCallsTask(&ran_task2, &deleted_task2)));
+
+  main_queue.Push(nested_queue.release());
+
+  // Run the task which pushes two more tasks.
+  main_queue.Run();
+
+  // None of the pushed tasks shoudl have run yet.
+  EXPECT_FALSE(ran_task1);
+  EXPECT_FALSE(deleted_task1);
+  EXPECT_FALSE(ran_task2);
+  EXPECT_FALSE(deleted_task2);
+  EXPECT_FALSE(main_queue.IsEmpty());
+
+  // Now run the nested tasks.
+  main_queue.Run();
+
+  EXPECT_TRUE(ran_task1);
+  EXPECT_TRUE(deleted_task1);
+  EXPECT_TRUE(ran_task2);
+  EXPECT_TRUE(deleted_task2);
+  EXPECT_TRUE(main_queue.IsEmpty());
+}